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A confidential security alert from security clearing house CERT has once again been leaked onto a full disclosure mailing list ahead of schedule.

The premature disclosure of information on security risks involving PDF files on *nix platforms comes after a spate of similarly leaked alerts back in March, including information about a vulnerability involving the Kerberos security protocol.

Once again an anonymous grey hat hacker/cracker, calling himself Hack4Life, is responsible for spilling the beans. Hack4Life posted a report of the flaw on a full disclosure mailing list last Friday ten days ahead of a planned release by CERT pencilled in for Monday, June 23. He also emailed journalists, including Register staffers, to publicise his exploits.

Hack4Life's motives remain unclear but general mischief, publicity seeking and an attempt to gain kudos in the digital underground seem to underlie his actions.

The leaked information contains an initial assessment of the vulnerability by Ohio-based security researcher Martyn Gilmore, who discovered the problem, which CERT had sent to vendors potentially affected by the issue.

This alert warns that "PDF files can contain malicious external-type hyperlinks that can execute arbitrary shell commands underneath Unix with various PDF viewers/readers."

"The hyperlinks must be activated or followed for the malicious script to run," the report adds.

The vulnerability could allow arbitrary shell commands to be executed on *nix boxes and is therefore potentially serious. Adobe Acrobat 5.06 and open-source reader Xpdf 1.01 are among the products affected, according to the report.

However, according to this early report, the vulnerability has not been coded up into script kiddie-friendly exploit.

Workarounds and/or fixes to address the vulnerability are yet to be produced and can't come a moment too soon. ®